Flexible, noncollapsible catheter tube with hard and soft regions

ABSTRACT

A unitary, flexible, substantially noncollapsible catheter tube of biocompatible material is comprised of hard and soft regions. The hard regions can be ring shaped or helical. The hard regions provide sufficient rigidity to the tube to prevent collapse under normal usage as the interior and exterior pressures vary. The soft regions provide sufficient flexibility to allow contoured placement of the tube. The hard regions can be created by exposing a polymer in the tube to radiation. The hard regions can also be created by periodically adding a harder material to the tube.

This application is a division, of application Ser. No. 07/734,478,filed on Jul. 23, 1991, now U.S. Pat. No. 5,222,949.

BACKGROUND OF THE INVENTION

Flexible tubing is used in many medical applications. The flexing of thetube permits contoured placement. In a medical context, flexible tubingis required for use in catheter devices to prevent damage when insertedinto a body lumen. However, flexible tubing has a continuing problemwith collapse. To prevent collapse, catheters require adequate stiffnessto effect insertion into the body lumen and to resist collapse as therespective interior and exterior pressures of the tube vary.

Catheter tubes are typically used for nasogastric suction, for theadministration of intravenous fluids and blood, for hemodialysis andother blood handling techniques, for gastro-duodenal feeding tubes,suction tubing, and tracheostomy tubing. Kinking of such tubing cancause blocking of the catheter. When kinking or suction induced collapseof the tube walls occur, flow ceases in the tubing and the consequencescan be serious--even fatal.

Knotting can also occur in tubing induced into a body cavity. Such knotsmake it impossible to withdraw the tubing without resorting to surgery.

Catheters can be a source of infection. This problem is exacerbated thelonger the catheter remains in the body. Organisms can enter the body atthe skin surrounding the catheter or through the interior of thecatheter.

SUMMARY OF THE INVENTION

Accordingly, a need exists in the medical field for tubing which isflexible yet includes adequate stiffness to prevent collapse duringnormal use. The invention is directed to a flexible, non-collapsibletube comprising a flexible region including a first composition and ahardened region of said first composition. The flexible region permitscontoured placement of the tube in a medical context. The hardenedregion of the tube provides sufficient rigidity to prevent collapse ofthe tube during long term use. In the preferred embodiment, the tube iscomprised of a polymer such as polyurethane with polybutadiene. Thehardened region can further comprise a plurality of ring shaped volumes.Also, the hardened region can comprise a helically shaped volume. Thehardened regions can be formed by exposing the tube to radiation. Thisradiation can be ultra-violet energy or thermal energy. The tube canfurther comprise additional radio-opaque material whenever necessary topermit positioning and placement under fluoroscopy and easierverification of position by a simple x-ray. Also, the hardened regionscan be hardened in vivo. A means can be provided to sterilize thecatheter in vivo. A second embodiment of the flexible, non-collapsiblecatheter for insertion in a body lumen can comprise a flexible regionincluding a first composition and a hardened region including a secondcomposition hardened by exposure to radiation.

The flexible tube of the invention can be manufactured by (a) extrudinga biocompatible plastic material having a substantially continuouscomposition to form a tubular plastic member and (b) exposing portionsof a plastic member to radiation to expose the hardened portions. Asnoted previously, the radiation can be ultraviolet energy or thermalenergy, but is not limited thereto. For example, ring shaped regions ofthe tube can be hardened to create a plurality of interspaced hardenedand flexible regions. Also, a helically shaped area of the tube can beexposed to produce a hardened portion in that shape.

Thus, a flexible, contourable tube is created with sufficient stiffnessand rigidity to resist collapse of the tube. The flexibility permitsaccommodation with the variation and the anatomic difference betweenpatients and prevents tissue damage by conforming to the vasculararchitecture of the individual. Moreover, the stiffness is sufficient topermit easy insertion and to prevent collapse of the tube. Thus,adequate blood flows are assured and adequate predictable fluid infusionrates over a broad range of clinical applications are permitted. Aspecific patient's requirements can be tailored at the bedside. Forexample, unlike conventional catheters which use a metallic coil toprovide tube hardening, a physician could insert a specific length ofthe catheter of the invention into a patient without exposing bodylumens to a sharp metal edge. The hardened areas assure obstructionprevention despite shifts in the patient's position and/or applicationof negative suction forces for sustaining high blood flow duringprocedures such as hemodialysis, hemofiltration, hemoprofusion, andplasmapheresis. The device is easy to manipulate and simple andinexpensive to manufacture. The device can also be used as aradio-opaque, low cost surgical drain.

The integral construction of the tube creates both a smooth interior, aswell as exterior, diameter. Thus, the tube is very compact. The simpleconstruction permits the use of inexpensive manufacturing techniques.

The above and other features of the invention including various noveldetails of the construction and combinations of parts will now be moreparticularly described with reference to the accompanying drawings aspointed out in the claims. It will be understood that the particulardevice embodying the invention is shown by way of illustration only andnot as a limitation of the invention. The principles and features ofthis invention will be employed in varied and numerous embodimentswithout departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1a illustrates the flexible, non-collapsible tube of the inventionwith ring shaped hardened areas.

FIG. 1b illustrates a longitudinal cross-sectional view of FIG. 1a.

FIG. 2a illustrates the flexible, non-collapsible tube of the inventionincluding a helically shaped hardened area.

FIG. 2b illustrates a longitudinal, cross-sectional view of theinvention of FIG. 2a.

FIG. 3 illustrates a horizontal, cross-sectional view of FIG. 2a.

FIG. 4 illustrates the placement of the flexible, non-collapsible tubeof the invention in a body lumen.

FIG. 4a illustrates the interior of the tube of the invention.

FIG. 5 illustrates an extrusion device for manufacturing the flexible,non-collapsible tube of the invention comprised of a hardened area ofthe same composition as the flexible area.

FIG. 6 illustrates an extrusion device for manufacturing a secondembodiment of the flexible, non-collapsible tube of the inventionincluding a flexible area comprised of a first material and a hardenedarea comprised of a second material.

FIG. 7(a) illustrates a longitudinal cross-sectional view of an in vivosterilization catheter.

FIG. 7(b) illustrates a horizontal cross-sectional view of the inventionof FIG. 7(a).

FIG. 7(c) is an enlarged view of the cross-section of FIG. 7(a).

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1a and 1b illustrate a first embodiment of the invention. FIG. 1ashows a schematic view of the flexible, noncollapsible biocompatibletube 30. Tube 30 is comprised of a hardenable polymer, such aspolyurethane with polybutadiene, which stiffens when exposed toultraviolet energy or thermal energy. As can be seen in FIG. 1a,flexible section 10, having a length B, provides adequate surface areato permit flexing of the tube around small radii curves. This allowsinsertion and placement without vascular wall injury or discomfort tothe patient. Moreover, the flexible volumes 10 are interspersed with thehardened volumes 20. These hardened regions provide sufficient stiffnessto prevent collapse which would result in the obstruction of the tubeopening or lumen. Thus, a tube constructed as shown in FIG. 1a can beused to infuse or suck fluids and blood products from veins, arteries,respiratory and congestive conduits for long periods of time.

Polyurethane, which is radioopaque, is useful in determining theplacement of the catheter. Other radioopaque materials could also beadded to the catheter to assist in locating the catheter position.

FIG. 1b shows the longitudinal cross-section of the schematicillustration of tube 30. As noted in the discussion of FIG. 1a, Brepresents the length of flexible section 10 and A represents the lengthof hardened section 20. The integral unitary composition of tube 30creates a compact, smooth walled coupling device.

Prior catheters used a soft polymeric tube structure with internallyreinforced stainless steel or polymeric springs. These springs increasedthe cost of the tubes substantially and reduced the efficiency of thetube by reducing the inner diameter and increasing the catheter wallthickness. By comparison, the interior and exterior diameters C and D,respectively, of the invention are constant along the length of the tube30. The length and caliber (or gauge) of the tube will depend on theintended application. Given its simplicity, flexibility and relative lowcost, construction can fit a gamut of applications for various lengthsand diameters.

The ratio of lengths A and B, will vary in accordance with the specificapplication. For instance, hemodialysis catheters would have a regularsequential structure whereby portions A would be discrete bands about1.5 mm wide alternating with portions B which would be discrete bandsabout 3 mm wide. The ratio of A/B would therefore be about 1/2 forhemodialysis applications.

In some instances, i.e. central lines for intravenous feeding and/ordrug infusion, the hardened portions need not be present along the wholelength of the catheter. Ideally, the hardened portions would berestricted to the indwelling (or inserted/intravascular) portion of thecatheter, hence allowing a highly flexible portion to extrude, whichwould be easy to fix or position, providing the patient with minimaldiscomfort.

FIGS. 2a and 2b illustrate a second embodiment of the flexible,noncollapsible tube 30. Both the flexible area 10 and the hardened area20 are in the shape of a helix. E and F represent the length of sections20 and 10 respectively along the longitudinal axis. The respective areasform an angle θ with the longitudinal axis of the tube 30. FIG. 2billustrates a longitudinal cross-sectional view of the embodiment ofFIG. 2a. As with the ring-shaped embodiment of FIGS. 1a and 1b, thehelical embodiment of FIGS. 2a and 2b create inner and outer diameterswhich are smooth along their longitudinal lengths. G represents theinner diameter of the tube whereas H represents the outer diameter ofthe tube.

FIG. 3 illustrates a horizontal cross-section of the tube of FIG. 2bwith a helical hardened section. As can be seen from FIG. 3, thehorizontal cross section reveals that hardened section 20 comprises asmall section of tube 30 with respect to the flexible section 10.

Medical tubes and catheters, surrounded as they are by live organs andtissues, are usually not subjected to a great deal of direct stress andstrain. The most "pressure" one can expect would be a patient's weight.

When a hollow tube of homogenous material is subjected to bending,material outside the bend radius of the neutral axis is subjected totensile stress proportional to its distance from the neutral axis.Conversely, material inside the neutral axis is subjected to compressivestress. These stresses cause the material to stretch and compress inaccordance with Hooke's law allowing bending to take place.

These stresses also impart a collapsing force on the tube proportionalto the ratio R_(t) /R_(b), where R_(t) is the radius of the tube andR_(b) is the radius of the bend. The ability of the tube to resist thiscollapsing force is proportional to the ratio R_(t) /W, where W is thewall thickness of the tube.

Therefore, in general terms, the non-collapsing force on the tube ofhomogeneous material is limited by the wall thickness of the tube; thesmaller the bend radius the thicker the wall that must be used.

In the case of a tube selectively reinforced by a spiral or a series ofrings of harder material, the collapse strength of the tube isincreased. This permits the use of a smaller bend radius and/or athinner walled tube than a tube of homogeneous material.

Some of the advantages of this type of tubing over homogeneous tubing asrelated to catheter usage are tighter bend radii for anatomicalplacement, larger inside diameter for a given outside diameterpermitting greater fluid flow, and increased collapse resistance frombody weight and vacuum aspiration.

FIG. 4 illustrates the placement of the flexible, noncollapsible tube ofthe invention. Section 110 illustrates target tissue which includes aportion of a small vessel, tortuous pathway which must be traversed toreach a selected target site. Vessel 112 branches into vessel 114 andvessel 116 branches from vessel 114. Tube 122 represents a flexible,noncollapsible catheter structure in accordance with the invention. Ascan be seen from FIG. 4, the catheter easily conforms to the tortuous,small blood vessel path. Moreover, the hardened sections of catheter 122prevents collapse regardless of the pressures residing at the interioror exterior of the tube.

The tube can be extruded in soft polyurethane and then submitted locallyto an intense ultraviolet light which would locally harden sections ofthe tube to a higher durometer, such as 80 or 90 Shore A. The tube wouldretain its original softness everywhere except in those areas that havebeen treated. Thus, the unhardened part of the tube will add theflexibility needed for adequate manipulation of the tube duringcatheterization procedures or to navigate around tight vascular corners.The hardened rings or helical sections will prevent the collapse of thetube under outside pressure. The tube's resistance to collapse permitslong term in vivo use. Localized heating could also create thisperfectly smooth plastic catheter which is flexible and noncollapsible.The hardened catheter can be removed from the patient by pulling on thedevice.

FIG. 4a illustrates the interior of the catheter 300 when in use in abody lumen 100. Fiber optic 15 can be used to transmit light to diagnosedisease, to ablate tissue, to harden the tube sections, and to sterilizethe catheter. Catheter 300 is comprised of hardened sections 201 andflexible sections 101.

FIGS. 5 and 6 illustrate inexpensive simple techniques for manufacturingflexible tubing with noncollapsible hardened sections. For example, FIG.5 shows an apparatus for creating a single composition tube. Extruder 40directs the plastic polymer material of the tube 30 along pipe 42 to atubing die 44. Unformed tube 46 is extruded from tubing die 44 and isconveyed to a radiation source 48. Radiation source 48 exposes portionsof unformed tube 46 to create hardened sections 20 interspersed withflexible sections 10. A source of thermal energy would be substitutedfor the radiation source 48. FIG. 5 shows the creation of ring shapedhardened regions. Radiation source 48 can also expose a helically shapedarea to harden a portion of tube 30 into a helix.

FIG. 6 illustrates an apparatus for making a flexible, noncollapsiblecatheter comprised of a first flexible material and a second hardermaterial. Extruder 40 forces a soft material through pipe 42 to thecasting/injection molder 54. Extruder 50 forces a harder second materialthrough pipe 52 to the casting/injection molder 54. The harder higherdurometer material is interspersed with the low durometer polyurethanefrom extruder 40. Tube 30 which is conveyed out of molder 54, is acomposite of the softer polyurethane areas 10 and the harder higherdurometer material areas 20. Radiation source 55 exposes the higherdurometer material in regions 20 and further hardens those segments ofthe catheter. As in the FIG. 5 embodiment, a source of thermal energycan be substituted for the radiation source 55. Also, a rotary dieextruder can be substituted for casting/injector molder 54 to produce aspiral or helical hardened area. By using a rotary die extruder, themain body of the tube is made of a soft material, extruded continuously,with a reinforcing spiral of a harder material pump in the main body ofthe tube to reinforce it.

FIGS. 7(a) and 7(b) illustrate a catheter which can be sterilized invivo. The transparent catheter 200 contains fiber optics 202 and 204along the length of its wall. The fiber optics can be fixed in the wallof the catheter or movable along the length of the catheter. The body ofcatheter 200 may, or may not be hardened in accordance with the previousdiscussions. The fiber optics 202 may be provided without cladding so asto let light escape axially. The fiber optics are connected to a sourceof ultraviolet light. To sterilize in vivo, a solution which conductsultraviolet light such as a saline solution is sent along the catheterinterior and the ultraviolet light is activated. The ultraviolet lightsterilizes the catheter interior and the body tissue surrounding thecatheter, especially tissue at the point of entry into the body. As aresult, the risk of infection is reduced. This five minute process needonly be performed once every twenty-four hours to be effective.Alternatively fiber optics can be provided with cladding 201 along itslength (as in fiber optic 202) or it can be segmented (as shown in theenlarged view of FIG. 7(c), wherein a portion 205 of the cladding 201 offiber optic 204 is removed around core 203). Thus, by moving the uncladportions of the fiber along the length of the catheter, selected areascan be sterilized or hardened.

FIG. 7(b) illustrates a horizontal cross sectional view of the catheterwith combined fiber optics. One or two fiber optics can be used forsterilization.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain, usingno more than routine experimentation, many equivalents to the specificembodiment described herein.

The invention is also applicable to tracheostomy or endotracheal tubing.These tubes can also be hardened in situ or in vivo after insertion withultraviolet light, beamed in a controlled segmental fashion to produceprecisely hardened segments to produce a molded tubing, adapted to agiven patient's anatomy. For example, dedicated optical fibers as inFIG. 7(a), with the cladding and which are moveable along the length ofthe catheter can be used to harden the tube at selected locations, aswell as to sterilize tissue at selected locations.

These and all other equivalents are intended to be encompassed by thefollowing claims.

I claim:
 1. A method of in vivo sterilization comprising:(a) positioningan optical fiber within a wall of a flexible, indwelling catheter; (b)positioning the catheter in a body lumen adjacent body tissue; and (c)transmitting ultraviolet light along the length of the optical fiber andradially outwardly from the fiber against the adjacent catheter so thatportions of the catheter and surrounding body tissue are exposed to theultraviolet light and sterilized.
 2. A method, as recited in claim 1,further comprising introducing a solution into the catheter which iscapable of conducting ultraviolet light.
 3. A method, as recited inclaim 2, in which the solution is saline solution.
 4. A method ofsterilization comprising:(a) positioning an optical fiber in a catheter;(b) positioning the catheter in a body; and (c) transmitting sterilizinglight along the length of the optical fiber and radially outwardly fromthe fiber against the adjacent catheter so that portions of the catheterare exposed to said light and sterilized.
 5. A method as recited inclaim 4 wherein the catheter is a flexible indwelling catheter.
 6. Amethod as recited in claim 4 wherein the catheter is positioned in apre-existing lumen of the body.
 7. A method as recited in claim 4wherein the optical fiber is positioned in a wall of the catheter.
 8. Amethod of in vivo sterilization comprising:(a) positioning an opticalfiber in a wall of a flexible, indwelling catheter; (b) positioning thecatheter in a body; (c) introducing a solution into the catheterconductive of ultraviolet light; and (d) transmitting said light alongthe length of the optical fiber and radially outwardly from the fiberagainst the adjacent catheter so that portions of the catheter areexposed to said light and sterilized.
 9. A method of in vivosterilization comprising:(a) positioning one or more optical fibers in aflexible, indwelling catheter; (b) positioning the catheter in bodytissue; and (c) transmitting sterilizing light along the length of oneor more of the optical fibers and radially outwardly from the fiberagainst the adjacent catheter so that portions of the catheter areexposed to the sterilizing light and sterilized.
 10. A method as recitedin claim 9 wherein the fiber is positioned in a wall of the catheter.11. The method of claim 9 wherein portions of body tissue adjacent thecatheter are also sterilized.
 12. A method of in vivo sterilizationcomprising:(a) positioning an optical fiber within a wall of flexible,indwelling catheter, said fiber being comprised of an inner core and anouter cladding layer with at least a portion of the cladding layerremoved; (b) positioning the catheter in a body lumen adjacent bodytissue; and (c) transmitting ultraviolet light along the length of theoptical fiber so that portions of the catheter and surrounding bodytissue opposite the removed cladding portion are exposed to theultraviolet light and sterilized.
 13. A method, as recited in claim 12,in which regions of the catheter exposed to said light emanating fromunclad portions of the optical fiber also become hardened.